Side effects and safety concerns

Because oral minoxidil acts systemically (throughout the whole body, not just on the scalp), it carries risks that topical minoxidil does not.

The most common side effect is hypertrichosis – unwanted hair growth on the face and body. This affects around 15 per cent of users and is more common in women and at higher doses.

For many people, hypertrichosis is manageable with regular hair removal, but it can be distressing and is a common reason for stopping treatment.

More significant side effects include fluid retention, low blood pressure causing dizziness and fainting, and an increased heart rate.

Oral minoxidil is contraindicated in people with cardiovascular disease, low blood pressure, significant kidney problems, and pregnancy – and yet these are conditions that a questionnaire-based online assessment may not be able to identify.

It is also worth noting that any hair gained with minoxidil will gradually be lost if the medicine is stopped. Customers should know this before they start.

Erectile dysfunction is the most common side effect of finasteride. Serious side effects are rare but include lumps, pain or swelling in the chest area, and low mood or depression.